Section 1 review
Energy can take many different forms: mechanical, radiant, nuclear, electrical, chemical, and thermal. Mechanical energy includes kinetic energy and potential energy (both gravitational and elastic). Work and energy are closely related, because energy is the ability to do work, and doing work on an object changes its energy. Potential energy is usually calculated in terms of a reference frame, in which a position of zero energy must be defined. Energy and work are both measured in joules (J). Read the text aloud
mechanical energy, work, joule (J), kinetic energy, potential energy, gravitational potential energy, reference frame, elastic potential energy, spring constant

E k = 1 2 m v 2
E p =mgh
E p = 1 2 k x 2

Review problems and questions

  1. What forms of energy are found in
    1. the Sun?
    2. a car’s engine? Read the text aloud Show
  1. A 30 kg boy sitting on a 10 kg go-kart wants to travel down a hill of height 10 m, starting from rest.
    1. What is the initial potential energy of the boy and go-kart together?
    2. What is their initial kinetic energy? Read the text aloud Show
  1. A 1,000 kg car traveling 15.0 m/s brakes and comes to a stop after traveling 20.0 m.
    1. What is the car’s initial kinetic energy?
    2. What is the car’s final kinetic energy?
    3. How much work does it take to stop the car?
    4. How much constant force is applied in bringing the car to a stop? Read the text aloud Show
  1. A baseball outfielder catches a fly ball traveling 25.0 m/s with his gloved hand. When he catches the 0.140 kg baseball, the outfielder’s hand recoils by 10.0 cm. How much force did the outfielder’s hand exert in catching the ball? Read the text aloud Show
  1. A horizontal spring with k = 100 N/m is compressed by 10 cm by a 100 g mass.
    1. How much elastic potential energy does the compressed spring store?
    2. How much elastic potential energy would the compressed spring store if it were compressed the same distance by a 300 g mass? Read the text aloud Show

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